1. Field of the Invention
The present invention relates to an apparatus and method for obtaining high pressures in an open flow reactor which, coupled with elevated temperatures, provides an efficient and economic way to effect aqueous pyrolysis and hydrolytic disproportionation of carbonaceous materials into liquid or gaseous hydrocarbons suitable for use as fuels. The invention incorporates deep wells to utilize high hydrostatic pressures resulting from the weight of the material being processed.
2. Related Art and Background
Pyrolysis reactions with carbonaceous solids (strong heating in a low-oxygen or oxygen-free environment) has a long history with numerous ‘town gas’ plants using the process to convert coal into gases that were then delivered via pipelines to customers in communities all over the country. These facilities were phased out within a decade of World War II as natural gas became widely available. Underground conversion of coal to gas or liquids is presently the subject of experimentation. Most of such experimentation involve some form of boring wells into a coal seam and initiating combustion at one. An oxidant such as air is introduced into the well and the gaseous pyrolysis products are removed at the other well. At the surface the gases can be used directly as fuel to generate electricity, or converted into a liquid such as methanol. Hydrocarbon liquids are produced only in small amounts with this technique.
Aqueous pyrolysis is an alternate method of direct recovery of energy recovery from coal. High temperature steam is introduced and a reaction results in the conversion of some coal into high-quality liquid hydrocarbons. Large amounts of energy are needed to provide the quantity and temperature of steam required to drive this reaction forward in the coal seam.
In another form, coal slurry is introduced into high pressure, high temperature reactors at the surface and yields a significant amount of liquid and gaseous hydrocarbons. In either case there exists a need for a technique to produce liquid and gaseous hydrocarbons from solid carbonaceous materials that is efficient in the percent conversion of raw material and sparing of the energy used in the conversion process. The in-situ (subsurface) processes appear to lose a significant fraction of the gross energy in the source materials and surface-based technologies are quite capital intensive, requiring a large and complex facility to generate the desired output of fuel hydrocarbons.
While aqueous pyrolysis is a chemical process that has been extant for several decades and thus is fairly well-known, hydrolytic disproportionation has only recently been recognized as a process of fundamental importance in the field of organic geochemistry which, among other things, deals with the formation of petroleum and natural gas from organic precursors in the rocks and sediments. For example, a 1991 paper in the publication Science by Siskin and Katritzky addressed the reactivity of organic compounds in heated water. This earlier work included the teaching that, in natural systems where kerogens are depolymerized, hot water is ubiquitous and usually contains salt and minerals. Reactions such as ionic condensation, cleavage, and hydrolysis are facilitated by changes in the chemical and physical properties of water as temperature increases. It was presented that such changes make the solvent properties of water at high temperature similar to those of polar organic solvents at room temperature, thus facilitating reactions with organic compounds.
No conclusions of the earlier investigators presented an application for the theories advanced, though it was suggested that an understanding of aqueous organic chemistry may lead to potential applications in areas as diverse as the recycling of plastics, the synthesis of chemicals, and coal liquefaction. The concept of hydrolytic disproportionation is a more recent concept that comes from literature dealing with the production and accumulation of oil and gas in sediments and sedimentary rock.
In 2001, L. C. Price prepared a chapter for a U.S. Geological Survey publication: Geologic Studies of Deep Natural Gas Resources. Price dealt with the generation of natural gas from deposits of “spent kerogen”—deposits that were supposedly done with the generation of hydrocarbons, but were still producing it anyway. The data from this early investigator supported a previous suggestion that water and high-rank, deeply buried, post-mature kerogen possibly undergo hydrolytic-disproportionation reactions with one another, resulting in the generation of high-rank methane-rich gas.
The Price reference taught that the term “hydrolytic disproportionation” of organic matter results from the premise that the water disproportionates into charged ions which then react with organic matter, which also disproportionates, to form an oxidized carbon species and a lower-molecular weight hydrocarbon, compared to the molecular weight of the starting organic matter.
Another important background article entitled “Organic-inorganic interactions in petroleum-producing sedimentary basins” was published in Nature (2003) by J. S Seewald. The target of this reference is not coal liquefaction specifically, but the chemistry and hydrolytic disproportionation processes discussed are germane to the technology of the present invention.
Such earlier investigations and background art approach the issue of HCC from the standpoint of oil or natural gas reservoirs, not the deliberate conversion of solid hydrocarbons into liquids and gases. The conclusion to be drawn from the above publications as well as many others in the art is that there exists a need for a means to economically apply high temperature and pressure water (perhaps as high as supercritical conditions) capable of reacting with complex carbon compounds to produce both liquid and gas-phase hydrocarbons.
At the same time it would be advantageous to develop a technique to produce liquid and gaseous hydrocarbons from solid carbonaceous materials that is sparing of the energy used in the conversion process. The in-situ (subsurface) processes of any present technology appear to lose a significant fraction of the gross energy in the source materials. Surface-based technologies are quite capital intensive, requiring a large and complex facility to get the desired output of fuel hydrocarbons.
It appears that the greatest obstacle to commercialization of such processes is, in large part, the high cost of installing and operating the high pressure/temperature reactors to bring about the conditions necessary to achieve aqueous pyrolysis and hydrolytic disproportionation. This problem coupled with the limited throughput of reactors operating in more or less ‘batch mode’ means a low overall yield for high costs of operation. Thus the key to a successful HCC process using these principles lies in development of a reactor that can sustain high temperatures and pressures together with a high-rate continuous throughput of raw material being subjected to the conditions that will convert the solid HC to liquid and gas fuels.
In the past, inventors have also realized that the hydrostatic pressure available at deep depths such as existing water or petroleum wells may be sufficient to produce pressures which far exceed what can be obtained in conventional apparatus using only mechanical pumping equipment to obtain such pressures. However, it has not been appreciated in the past that such pressures obtainable in deep boreholes may be used to improve the processing identified in the present disclosure. For example, U.S. Pat. Nos. 3,606,999 issued in 1971 and 4,416,956 issued in 1983, both to Lawless, describe apparatus for carrying out a chemical or physical process, identifies the usefulness of a deep borehole, but applies such usefulness only for fuel cells to use a chemical reaction for producing electricity. Lawless identifies the usefulness of deep boreholes for certain processes but fails to realize or teach the application or possible use to perfect hydraulic disproportionation of a coal slurry or similar material into liquid or gaseous hydrocarbons. Further, any prior art does not teach introduction of energy into the system to process slurry at the point in which it flows into the reactor zone.